Developing countries have long been a unified bloc, demanding that industrialized nations take most of the responsibility for cutting global greenhouse gas emissions. But faced with the fact that a handful of emerging economies — led by China and India — are helping drive carbon emissions to new heights, the world’s smallest nations joined forces with the European Union to demand decisive action from their former allies as well as the United States.

The Durban agreement provides countries with the latitude to forge something that would apply to all nations, called an “agreed outcome with legal force,” a last-minute compromise that creates a less stringent alternative to a traditional treaty. Several experts said such an agreement would be stronger than the voluntary accords reached last year in Cancun, Mexico.

Ned Helme, who heads the Washington-based Center for Clean Air Policy, said the provision means “it is enforceable and makes countries accountable. Of course, we know that international law is a lot less enforceable than domestic laws.”

Jake Schmidt, international climate policy director for the Natural Resources Defense Council, called the agreement “important progress,” adding, “this outcome brings large countries like China and India into the room to negotiate meaningful commitments to address the urgent need to cut global emissions.”

This year’s U.N. meeting took on greater significance because it comes as the world’s only existing climate treaty, the 1997 Kyoto Protocol, is reaching the end of its first commitment period.

E.U. officials maintained that they would be willing to extend emission cuts under the Kyoto accord only if all the world’s major emitters agreed to negotiate a new legally binding climate pact.

Connie Hedegaard, E.U. commissioner on climate action, who had characterized an earlier version of the package as too weak, said “an agreed outcome with legal force” is “ a good and strong result.”

Representatives of small nations, such as I.J. Karl Hood, Grenada’s minister of foreign affairs, environment, foreign trade and export development, had endorsed the E.U.’s insistence on strong terms for the agreement. “We cannot allow countries to continue on the track which has brought us to this place,” he said. “. . . While they develop, we die in the process. Madam Chair, why should we accept this? Why?”

Initially, India’s minister for environment and forests, Jayanthi Natarajan, had fought for language to give developing countries such as hers more flexibility.

“This is not about India. This is about the world,” she said. “Does climate change mean you give up equity? What is the problem with adding one more option? What is the problem?

But after saying she was unwilling to “sign away the rights of 1.2 billion people” for the sake of securing a global climate deal, Natarajan agreed to modify the provision.

While the United States had come under fierce criticism throughout the meeting because it objected to the idea of negotiating a legal treaty, by the end the Obama administration agreed to endorse a process aimed at securing a binding treaty or “legal instrument,” a term slightly stronger than the actual final language.

Delegates to the U.N. Framework Convention on Climate Change (UNFCCC) were unanimous in calling for a cut in global greenhouse gas emissions before the end of the decade. But they remained divided until the very end on whether to stick with the historic framework — in which industrialized nations committed to binding cuts and financed voluntary actions by developing countries — or to forge a new one.

World events and new scientific and economic projection helped reshape nations’ negotiating positions in Durban as delegates from the E.U. and the developing world alike said they could no longer afford delay.

Though delegates did manage to sketch out details on how to administer money for poor countries affected by climate change and help transfer clean technology to developing nations, environmentalists said the Durban package still fell short of the ambitious cuts needed to avert dangerous warming.

New scientific findings have made it clear that any effort to curb emissions without meaningful cuts from major emerging economies will fail to keep the global temperature increase below 2 degrees Celsius (3.6 degrees Fahrenheit). ­UNFCCC delegates have pledged to limit the temperature rise to 2 degrees Celsius, above which, scientists warn, there could be disastrous climate impacts.

Last month, the International Energy Agency projected the world was on a path to reach 6 degrees Celsius (10.8 degrees Fahrenheit) above preindustrial levels by 2100. Last week, researchers from the Wilhelm Bjerknes Centre in Bergen, Norway, gave a presentation in Durban projecting that the Arctic will experience a 2-degree temperature increase within one to two decades. The only way to limit the global increase to 2 degrees, the researchers said, was to have global emissions peak by 2020 and fall between 40 percent and 50 percent between 2040 and 2050.

“That’s the real missing element here,” said Alden Meyer, director of strategy and policy at the Union of Concerned Scientists. “There’s nothing that’s going to get the world to lift its game and close that gap.”

While some green groups were even harsher — Friends of the Earth International issued a release saying “the noise of corporate polluters has drowned out the voices of ordinary people in the ears of our leaders” — host country South Africa cheered the outcome. “We have indeed saved tomorrow today,” said South Africa’s foreign minister Maite Nkoana-Mashabane.

Juliet Eilperin is The Washington Post's White House bureau chief, covering domestic and foreign policy as well as the culture of 1600 Pennsylvania Avenue. She is the author of two books—one on sharks, and another on Congress, not to be confused with each other—and has worked for the Post since 1998.

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